VirtualBox

Oracle’s VirtualBox is suitable for both home and commercial use. This set of x86 products for virtualization is remarkably rich in features. It is a top performing product suitable for enterprise clients, yet it is surprisingly the one and only pro solution to be available as free of charge Open Source via GNU.

VirtualBox is typically run on Linux, Windows, and Mac OSX. However, it also supports a raft of other operating systems such as DOS, Linux versions 2.4 & 2.6, Windows 3, plus OpenBSD, among others.